AAMOF, the waveform between the outside track and the earth ground will alternate at 455khz, the frequency of the TMCC carrier. From a Legacy or BASE1L, the amplitude of the waveform will be between 5v P-P and 6v P-P. For the older TMCC BASE1, the amplitude will be between 3v P-P and 4v P-P. That's one reason that upgrading to Legacy helps many layouts, it's simply a stronger TMCC signal.
The TMCC Buffer is capable of boosting that TMCC signal to around 15v P-P, and also drives it with a low impedance amplifier to allow it to drive a lot more capacitance or lower resistance between the earth ground and outside tracks. This makes TMCC possible in places like the New Jersey High Railers massive layout.
